Thomas Le Seur

Thomas Le Seur OFM (born October 1, 1703 in Rethel , France , † September 26, 1770 in Rome ) was a French mathematician and physicist.

Le Seur was a Franciscan priest and professor of mathematics at the College for Propaganda ( Congregation for the Evangelization of Peoples ) in Rome. With his professor colleague François Jacquier (1711–1788, also Jaquier), also a Franciscan, he published a new edition of Isaac Newton's “ Philosophiae Naturalis Principia Mathematica ” with detailed commentary, which appeared in Geneva from 1739 to 1742 , and on which other scientists also collaborated . In the comments, deductions with methods of infinitesimal calculus were given in continental European form according to the Leibniz calculus (Newton himself presented his proofs in the Principia using classical geometric methods). They also wrote an analysis textbook (Memoir sur le calcul intégral, Rome, 1748).

Both are also known for the fact that they wrote the first static report for the restoration of the dome of St. Peter's Basilica together with the Jesuit scientist Ruger Boscovich in 1742. This was described by Hans Straub as the "birth of modern civil engineering". Before that, mathematical calculations were not common in civil engineering and the use of mathematics in the renovation of Michelangelo's dome was promptly criticized by contemporaries. Cracks had formed in the dome, and the calculations of the three mathematicians came to the conclusion that the existing circular pull rings that were supposed to absorb the vault thrust were insufficiently dimensioned. They published their work in 1743 ( Parere di tre mattematici sopra i danni che si sono trovati nella Cupola di S. Pietro sul fine de l'anno 1742 ). The Pope also commissioned another expert opinion from the professor in Padua (and hydraulic engineer for the Republic of Venice) Giovanni Poleni , which was of a completely different opinion regarding the causes (Poleni blamed earthquakes, uneven loads and thus subsidence, lightning strikes), but also recommended reinforced pull rings.

In the annotated Newton edition by Jacquier and Le Seur from 1742 there is also the experimental and theoretical proof that the force of a magnet decreases with it ( dipole field). This behavior was already assumed by Newton in the second edition of his Principia of 1713, but direct experimental evidence was not available to him. The experiments carried out at Newton's suggestion by Francis Hauksbee , Brook Taylor and Edmund Halley in 1712 (or even earlier those of Robert Hooke ) were inconclusive. Newton also gave no derivation of the cubic law of force. This only happened in the edition of Jacquier and Le Seur, whereby this commentary on Corollary 5, Proposition 6 in Book 3 of Newton's Principia probably comes from Jean-Louis Calandrini (1703-1758), a professor at the University of Geneva who also the Conducted experiments. ${\ displaystyle {\ frac {1} {r ^ {3}}}}$

Le Seur was a corresponding member of the Académie des Sciences since 1745 and an external member of the Berlin Academy of Sciences since 1749 .

Riflessioni sopra alcune difficoltà spettanti i danni e risarcimenti della cupola di S. Pietro , 1743

literature

Istvan Szabo History of Mechanical Principles , Birkhäuser 1987
Hans Straub History of Civil Engineering , Birkhäuser 1992,
D.Conrad, T.Hänseroth The "hour of birth of modern civil engineering" 250 years ago and its prehistory , Bautechnik Vol. 70, 1993, p. 176
Karl-Eugen Kurrer : The History of the Theory of Structures. Searching for Equilibrium . Ernst & Sohn , Berlin 2018, pp. 921ff., ISBN 978-3-433-03229-9 .

Web links

Wapenhans, Richter “The world's first statics from 1742 for St. Peter's Dome in Rome”, PDF file (555 kB)

Remarks

↑ Sometimes also written reading
↑ Jacquier is mentioned with praise in Goethe's Italian Journey
↑ In the end result, however, they underestimated the remaining load-bearing capacity of the dome in their two-dimensional approximation, as a finite element recalculation showed. Norbert Friedl, diploma thesis at the Institute for Structural Analysis at TU Graz with Gernot Beer, 2004
↑ 1748 published as Memorie istoriche della Gran Cupola del Tempio Vaticano
^ H. Ricker III Magnetism in the 18th century .
^ List of members since 1666: Letter L. Académie des sciences, accessed on January 12, 2020 (French).

personal data
SURNAME	Le Seur, Thomas
BRIEF DESCRIPTION	French mathematician and physicist
DATE OF BIRTH	October 1, 1703
PLACE OF BIRTH	Rethel , France
DATE OF DEATH	September 26, 1770
Place of death	Rome

[1] Sometimes also written reading

[2] Jacquier is mentioned with praise in Goethe's Italian Journey

[3] In the end result, however, they underestimated the remaining load-bearing capacity of the dome in their two-dimensional approximation, as a finite element recalculation showed. Norbert Friedl, diploma thesis at the Institute for Structural Analysis at TU Graz with Gernot Beer, 2004

[4] 1748 published as Memorie istoriche della Gran Cupola del Tempio Vaticano

[5] H. Ricker III Magnetism in the 18th century .

[6] List of members since 1666: Letter L. Académie des sciences, accessed on January 12, 2020 (French).